1. Field of the Invention
The present invention relates to information recording, and more particularly to information recording on a recording medium such as a CD-R (compact disk recordable) or a CD-RW (compact disk rewritable) by an information recording apparatus such as an optical disk unit.
2. Description of the Related Art
In a recording medium such as a magneto-optical (MO) disk or an MD (Mini Disc), data is written to the recording medium in small units so that data once recorded thereon can be rewritten. When a failure occurs in writing, recovery from the failure can be made by performing another normal writing operation. In some non-rewritable recording media, recovery from failure can be achieved by a replacement operation by which the defective sector including a failure is replaced by another normal sector.
However, in the case of a recording medium on which data is recorded with a CD format with no writing unit, such as the CD-R, there is no effective means for recovering from failure in writing. Therefore, as has been the case for a long time, the recording medium becomes unusable only to be discarded if a failure occurs during data writing.
Although the CD-R has such a disadvantage, its low price and high compatibility in reproduction has made the CD-R extremely popular. Further, the disadvantage of the CD-R has been eliminated recently.
Japanese Laid-Open Patent Application No. 2001-67819 and Japanese Published Examined Application No. 7-31904 disclose technologies for preventing a buffer under-run by suspending and then resuming recording, and optical disk drives preventing the occurrence of a buffer under-run error, which can be the largest factor of recording failure, have been already provided. Here, the buffer under-run refers to a state where the rate of writing data supplied from a buffer is higher than the rate of transferring data to the buffer so that data stored in the buffer runs short.
There are many other factors of (or causes for) recording failure than the buffer under-run. Vibration and impact, for instance, are factors that cannot be overlooked.
In the case of the occurrence of an impact or a vibration, recording failure can be avoided by first suspending recording at the point of detecting the impact or vibration before the impact or vibration causes a “servo error” (a condition in which a servosystem, or a laser spot, is off track and/or out of focus) or the deterioration of recording quality and then resuming the recording when the impact or vibration disappears. Therefore, by using the above-described technologies of preventing the buffer under-run by suspending and then resuming data recording, recording failure resulting from vibration or impact can be avoided.
The problem, however, is the time lag between the issuance of an instruction to suspend recording and the actual stopping of the recording. If there is a time lag between the occurrence of a recording failure and the suspension of recording, data corresponding to that period is lost. Therefore, the time lag should be minimized.
According to the above-described conventional technologies, there is a fairly long period of time between the detection of a buffer under-run error and the suspension of recording. Therefore, it is sufficient if recording is suspendable by the sector. The direct application of this technique, however, may cause the loss of data for approximately one sector or lead to miswriting of data to the adjacent track, depending on the timing of the occurrence of impact or vibration.